This invention relates to stabilizer compositions comprising degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, said products including a free mercaptan. This invention also relates to polymer compositions containing a polymer normally susceptible to heat-induced deterioration and the degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, said products including a free mercaptan. It also relates to such polymer compositions further containing a metallic-based heat stabilizer. This invention also relates to articles of manufacture, e.g. pipe, film, and window profile, made from stabilized polymer compositions containing a polymer normally susceptible to heat-induced deterioration, the degradation products of a blocked mercaptan present during processing of the composition at an elevated temperature, saidxe2x80x94based heat stabilizer. Another aspect of this invention is the development of a novel reaction scheme which, although crude, affords latent mercaptans which need no purification to be highly active PVC heat stabilizers at low use levels.
This invention also relates to latent mercaptans which are substantially free of the offensive odor typical of mercaptans and which may be used as anti-oxidants, odorants, anti-microbial agents, chelating agents and photostabilizers; and as intermediates for the preparation of anti-oxidants and primary heat stabilizers. It also relates to such anti-oxidants and primary heat stabilizers.
It is well known that the physical properties of various organic polymers deteriorate and color changes take place during processing of the polymer and during exposure of formed polymer products to certain environments. The prime examples of polymers which are susceptible to degradation during processing are the halogen-containing polymers such as the vinyl and vinylidene polymers in which the halogen is attached directly to carbon atoms. Poly(vinyl chloride) or PVC, copolymers of vinyl chloride and vinyl acetate, and poly(vinylidene chloride), the principal resin in self-clinging transparent food wraps, are the most familiar polymers which require stabilization for their survival during fabrication into pipes, window casings, siding, bottles, and packaging film, etc. When such polymers are processed at elevated temperatures, undesirable color changes often occur within the first 5 to 10 minutes as well as during later stages of the processing. Haziness, which sometimes accompanies the color changes, is particularly undesirable where clear products are needed. The addition of heat stabilizers to such polymers has been absolutely essential to the wide-spread utility of the polymers. From a great deal of work in the development of more and more effective heat stabilizers there has emerged two principal classes: organotin compounds and mixed metal combinations. Organotin-based heat stabilizers are the most efficient and widely used PVC stabilizers. Synergistic combinations of alkyltin mercaptides and free mercaptans are particularly efficient heat stabilizers for PVC during extrusion. They have not been entirely satisfactory, however, because of several failings on the part of the mercaptan synergist. Many mercaptans give off an offensive odor even at room temperature and the odor grows worse at PVC processing temperatures. The oxidative stability of the mercaptans is very often very poor. Oxidation of the free mercaptans diminishes the synergism. Thus, a combination having an enhanced synergism would be welcomed by the PVC industry. Also, because of the end-use of articles made from some polymers, many polymeric compositions require the presence of both biocides and heat stabilizers but the use of the organotin mercaptide/mercaptan combination in such a composition is often frustrated by the tendency of the free mercaptan to deactivate a biocide such as the much used OBPA (10,10xe2x80x2-oxybisphenoxarsine).
In U.S. Pat. No. 3,660,331, Ludwig teaches the stabilization of vinyl halide resins by certain thioethers and thioesters of tetrahydropyran. Better heat stabilizer compositions are still needed, however. The thioethers of this invention satisfy that need.
It is an object of this invention, therefore, to provide a heat stabilizer composition having the synergy of a mercaptan plus improved oxidative stability.
It is another object of this invention to provide a latent mercaptan-containing heat stabilizer composition which is substantially free from the offensive odor typically associated with mercaptans.
It is a related object of this invention to provide a latent mercaptan-containing heat stabilizer composition which has a decidedly pleasant odor.
It is a further object of this invention to provide an improved polymeric composition containing a biocide and a latent mercaptan-containing heat stabilizer.
It is a related object of this invention to provide a polymeric composition containing a heat stabilizer combination having the synergy of a mercaptan plus improved oxidative stability.
It is still another object of this invention to provide latent mercaptans as intermediates for the preparation of anti-oxidants, anti-microbial agents, photostabilizers, and primary heat stabilizers.
These and other objects of the invention which will become apparent from the following description are achieved by incorporating into a polymeric composition containing a polymer normally susceptible to heat-induced deterioration a blocked mercaptan which degrades during processing of the composition at an elevated temperature to liberate a free mercaptan. The latent mercaptan may act as the sole heat stabilizer but the free mercaptan may also synergize the activity of other heat stabilizers in the composition. Other products of the degradation of the blocked mercaptan are believed to include carbocations of the blocking moiety which are stabilized by a molecular structure in which the electron deficiency is shared by several groups. Resonance stabilization and neighboring group stabilization are two of the possible mechanisms by which the carbocations may be stabilized. The carbocations act as intermediates in the formation of stable compounds early in the hot processing of halogen-containing polymers. Although such mechanisms and the resultant carbocations are believed to be an impetus for the liberation of the active free mercaptan, this invention is in no way limited by the foregoing attempt to explain the working of the invention. Those skilled in the art will see the resonance stabilization and neighboring group stabilization that are possible in the following structures of the blocked mercaptan; other mechanisms may be at work in other blocked mercaptans represented by these structures that also liberate an active free mercaptan upon thermal and/or chemical degradation during processing of polymeric compositions containing such blocked mercaptans. For the purposes of this invention, the terms xe2x80x9cblocked mercaptanxe2x80x9d and xe2x80x9clatent mercaptanxe2x80x9d are used interchangeably to mean a thioether which degrades during processing of the composition at an elevated temperature to liberate a free mercaptan.
The stabilizer compositions of the present invention may comprise a metal-based stabilizer and such a latent mercaptan or mixture of latent mercaptans.
As used herein: the terms xe2x80x9cgroupxe2x80x9d and xe2x80x9cradicalxe2x80x9d are used interchangeably, a mono-valent radical has but one valence available for combining with another radical whereas a di-valent radical may combine with two other radicals; the term alkyl represents monovalent straight or branched chain hydrocarbon radicals containing, for example, 1 to 20 carbon atoms; the term alkylenyl represents divalent, trivalent, and tetravalent straight or branched chain hydrocarbon radicals containing, for example, 1 to 20 carbon atoms; the term aryl represents monovalent C6-C10 aromatic rings such as benzene and naphthalene; the term alkenyl represents monovalent straight or branched chain C2 to C20 hydrocarbon radicals containing at least one double bond; the term aralkyl represents a monovalent C1 to C20 hydrocarbon radical having attached thereto an aryl radical; the term alkaryl represents monovalent aryl radicals having attached thereto at least one C1-C20 alkyl group; the term cycloalkyl represents monovalent C3-C8 saturated cycloaliphatic radicals; the term cycloalkenyl represents C5-C8 cycloaliphatic radicals containing at least one double bond; the term polyalkoxy means a chain of from 2 to 6 alkoxy groups wherein the alkoxy group is ethoxy, propoxy, isopropoxy, butoxy, or the like, with or without an end group such as hydroxy, acyloxy, benzyloxy, benzoyloxy, butoxy, and tetrahydropyranyloxy; the term halogen-containing organic polymers represents halogen-containing vinyl and vinylidene polymers or resins in which the halogen is attached directly to the carbon atoms.
Also, as used herein: an acyloxyalkyl radical originates from a carboxylic acid ester of an alkyl alcohol; the R1 radical in Formula 1 below, therefore, in the stearic acid ester of mercaptopropanol is the stearoyloxypropyl radical; likewise, the R1 radical of the oleic acid ester of mercaptopropanol, which is one the tallate esters of that alcohol, is the oleoyloxypropyl radical; the R1 radical of lauryl-3-mercaptopropionate, on the other hand, is dodecyloxy-carbonylpropyl.
The polymeric compositions of this invention contain polymers normally susceptible to heat-induced deterioration such as the above-noted halogen-containing polymers. The stabilizer compositions of this invention are particularly suited to impart a superior stabilization against the deteriorative effects of heat and ultra-violet light on halogen-containing organic polymers compared to that imparted by stabilizer compositions previously known in the art.
The halogen-containing organic polymers which can be stabilized according to this invention include chlorinated polyethylene having 14 to 75%, e.g. 27%, chlorine by weight, chlorinated natural and synthetic rubber, rubber hydrochloride, chlorinated polystyrene, chlorinated polyvinyl chloride, polyvinyl bromide, polyvinyl fluoride, copolymers of vinyl chloride with 1 to 90%, preferably 1 to 30%, of a copolymerizable ethylenically unsaturated material such as, for example, vinyl acetate, vinyl butyrate, vinyl benzoate, vinylidene chloride, diethyl fumarate, diethyl maleate, other alkyl fumarates and maleates, vinyl propionate, methyl acrylate, 2-ethylhexyl acrylate, butyl acrylate and other alkyl acrylates, methyl methacrylate, ethyl methacrylate, butyl methacrylate and other alkyl methacrylates, methyl alpha-chloroacrylate, styrene, trichloroethylene, vinyl ethers such as vinyl ethyl ether, vinyl chloroethyl ether and vinyl phenyl ether, vinyl ketones such as vinyl methyl ketone and vinyl phenyl ketone, 1-fluoro-2-chloroethylene, acrylonitrile, chloroacrylonitrile, allylidene diacetate and chloroallylidene diacetate. Typical copolymers include vinyl chloride-vinyl acetate (96:4 sold commercially as VYNW), vinyl chloride-vinyl acetate (87:13), vinyl chloride-vinyl acetate-maleic anhydride ((86:13:1), vinyl chloride-vinylidene chloride (95:5); vinyl chloride-diethyl fumarate (95:5), and vinyl chloride 2-ethylhexyl acrylate (80:20). In addition to the stabilizer compositions of this invention, there can also be incorporated into the halogen-containing organic polymer conventional additives such as plasticizers, pigments, fillers, dyes, ultraviolet light absorbing agents, densifying agents, biocides and the like.
Preferably, the halogen-containing organic polymer is a vinyl halide polymer, more particularly a vinyl chloride polymer. Usually, the vinyl chloride polymer is made from monomers consisting of vinyl chloride alone or a mixture of monomers comprising, preferably, at least about 70% by weight based on the total monomer weight of vinyl chloride.
FORMULA 1 is representative of the blocked mercaptans that are suitable for the purposes of this invention: 
wherein a is 0 or 1, m and n are 0 or 1; y=1 to 4; when y=1, z is 1 to 4; and when y is more than 1, z is 1; R1 is an alkyl, alkylenyl, cycloalkyl, cycloalkylenyl, aryl, alkaryl, aralkyl, aralkylenyl, hydroxyalkyl, dihydroxyalkyl, hydroxy(polyalkoxy)alkyl, alkoxyalkyl, hydroxyalkoxyalkyl, alkoxy(hydroxyalkyl), alkoxy(acyloxyalkyl), alkoxy(polyalkoxy)alkyl, alkoxy(polyalkoxy)carbonylalkyl, carboxyalkyl, acyloxyalkyl, acyloxy(hydroxyalkyl), acyloxyalkoxyalkyl, acyloxy(polyalkoxy)alkyl, benzoyloxy(polyalkoxy)alkyl, alkylenebis-(acyloxyalkyl), alkoxycarbonylalkyl, alkoxycarbonylalkylenyl, hydroxyalkoxycarbonylalkyl, hydroxy(polyalkoxy)carbonylalkyl, mercaptoalkyl, mercaptoalkylenyl, mercaptoalkoxycarbonylalkyl, mercaptoalkoxycarbonylalkylenyl, alkoxycarbonyl(amido)alkyl, alkylcarbonyloxy(polyalkoxy)carbonylalkyl, tetrahydopyranyloxy(polyalkoxy)carbonylalkyl, tetrahydropyranyloxyalkyl, hydroxyaryl, mercaptoaryl or carboxyaryl radical having from 1 to 22 carbon atoms; R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, acyl, alkyl, alkylenyl, aryl, haloaryl, alkaryl, aralkyl, hydroxyalkyl, mercaptoalkyl, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, mercaptoaryl groups having from 1 to 22 carbon atoms; X is aryl, haloaryl, alkaryl, hydroxyaryl, dihydroxyaryl, alkoxyaryl, arylcycloalkyl, or a heteroatom, with the option that when a is 1 and m is 1, R6 and R7 form a heterocyclic moiety in conjunction with X as nitrogen, and with the further option that when a=1 and m=0, one of R1, R3, and R5 joins with R7 and X to form a heterocyclic moiety with X as a heteroatom selected from the group consisting of oxygen and sulfur; with the proviso that z is 1 or 2 when X is aralkaryl, R6 and R7 are hydroxyl, a is 1 and m is 1, and with the further proviso that when R6; hydroxyl or mercapto, z is 1.
A polymeric composition wherein the blocked mercaptan has the following structure is another embodiment of this invention: 
wherein a is 0 or 1, m and n are 0 or 1; y=1 to 4, when y=1, z is 1 to 4 when y is more than 1 z is 1; R1 is an an alkyl, alkylenyl, cycloalkyl, cycloalkylenyl, aryl, alkaryl, aralkyl, aralkylenyl, hydroxyalkyl, dihydroxyalkyl, hydroxy(polyalkoxy)alkyl, alkoxy(polyalkoxy)carbonylalkyl, alkoxyalkyl, hydroxyalkoxyalkyl, alkoxy(hydroxyalkyl), alkoxy(acyloxyalkyl), alkoxy(polyalkoxy)alkyl, carboxyalkyl, acyloxyalkyl, acyloxy(hydroxyalkyl), acyloxyalkoxyalkyl, acyloxy(polyalkoxy)alkyl, benzoyloxy(polyalkoxy)alkyl, alkylenebis-(acyloxyalkyl), alkoxycarbonylalkyl, alkoxycarbonylalkylenyl, hydroxyalkoxycarbonylalkyl, hydroxy(polyalkoxy)carbonylalkyl, mercaptoalkyl, mercaptoalkylenyl, mercaptoalkoxycarbonylalkyl, mercaptoalkoxycarbonylalkylenyl, alkoxycarbonyl(amido)alkyl, alkylcarbonyloxy(polyalkoxy)carbonylalkyl, tetrahydopyranyloxy(polyalkoxy)carbonylalkyl, tetrahydropyranyloxyalkyl, hydroxyaryl, mercaptoaryl or carboxyaryl radical having from 1 to 22 carbon atoms; R2, R3, R4, R5, R6, and R7 are independently hydrogen, a hydroxyl, mercapto, alkyl, alkylenyl, aryl, haloaryl, alkaryl, aralkyl, hydroxyalkyl, mercaptoalkyl, hydroxyalkylmercaptoalkyl, mercaptoalkylenyl, hydroxyaryl, alkoxyaryl, alkoxyhydroxyaryl, arylcarbonyl, or mercaptoaryl radical having from 1 to 22 carbon atoms; when a=1, X is arylcycloalkyl or a heteroatom, and when a=0, X is aryl, haloaryl, alkaryl, alkoxyaryl, arylcycloalkyl, or a heteroatom, with the option that when a is 1 and m is 0, one of R3 and R5 joins with R7 and X to form a heterocyclic moiety with X as a heteroatom selected from the group consisting of oxygen and sulfur, and with the further option that when a is 1 and m is 1, R6 and R7 form a heterocyclic moiety in conjunction with X as a nitrogen atom.
The mercaptan-containing organic compounds which may be converted into latent mercaptans for the purposes of this invention are well-known compounds and include alkyl mercaptans, mercapto esters, mercapto alcohols, and mercapto acids. See, for example, U.S. Pat. Nos. 3,503,924 and 3,507,827. Alkyl mercaptans having from 1 to about 200 carbon atoms and from 1 to 4 mercapto groups are suitable. Mercaptan-containing organic compounds which include R1 have structures illustrated by the following formulas: 
wherein R10 and R19 are the same or different and are 
R11 is xe2x80x94H, aryl, or C1 to C18 alkyl;
R12 is cycloalkyl, cycloalkenyl or phenyl;
R13 is 
xe2x80x94SH, aryl Cito C18 alkyl, xe2x80x94OH or xe2x80x94H.
with the proviso that in formula (MC2) when R12 is phenyl, R13 is xe2x80x94OH and i=0, then the xe2x80x94SH groups are on non-adjacent carbon atoms;
R14 is xe2x80x94H or a divalent group which may contain halogen, hydroxy, mercapto or alkyl substituents and which when R12 is phenyl combines with the phenyl to form a naphthalene ring;
R15 is 
R16 is xe2x80x94CH3, xe2x80x94H2CH3, or 
R17 is xe2x80x94H, or alkyl, alkenyl, aryl, aralkyl, alkaryl, cycloalkyl, cycloalkylenyl;
R18 is arylene, C1 to C8 alkylenyl, 
wherein b is an integer from 1 to 6;
i=0 or an integer from 1 to 6 inclusive;
j=0, 1, 2 or 3; and
f=1 or 2.
Mercaptan-containing organic compounds preferred as intermediates in the preparation of the latent mercaptans of this invention are those compounds according to formula (MC1) where R11 is xe2x80x94H, R19 is xe2x80x94H, R10 is OH or 
and i=1; those compounds according to formula (MC2) where R12 is phenyl, R11 is xe2x80x94H, R13 is xe2x80x94H, R14 is xe2x80x94H, i=1, and j=1; those compounds according to formula (MC3) where R11 is xe2x80x94H, R15 is 
and i=1; those compounds according to formula (MC4) where R11 is xe2x80x94H and i=1; those compounds according to formula (MC5) where R16 is xe2x80x94C2H5 or 
R11 is xe2x80x94H and i=1; and those compounds according to formula (MC6) where R11 is xe2x80x94H and i=1.